Welcome to the 21st Edition of Nelson Textbook of Pediatrics – the reference of choice among pediatricians, pediatric residents, and others involved in the care of young patients. This fully revised edition continues to provide the breadth and depth of knowledge you expect from Nelson, while also keeping you up to date with new advances in the science and art of pediatric practice. Authoritative and reader-friendly, it delivers the information you need in a concise, easy-to-use format for everyday reference and study. From rapidly changing diagnostic and treatment protocols to new technologies to the wide range of biologic,